A sabot is used to propel a subcaliber projectile at high velocity from a gun barrel. Its function is to increase the effective area against which the propellant gas pressure may act to propel the projectile. In modern projectile designs, particularly those in the armor piercing class, the sabot also provides significant structural support to the sub-projectile as it is accelerated through the gun barrel. It is also desirable for a sabot to be light in weight since energy which is required to propel the sabot is not imparted to the sub-projectile.
Prior art sabot designs have attempted to provide both structural support and minimum weight. For example, the sabot of Kirkendall et al., U.S. Pat. No. 4,284,008, teaches a double ramp design with a centrally positioned obturating band seat to eliminate the necessity for an excessively heavy boreriding support, like those used in prior art saddle back designs such as that of Luther et al., U.S. Pat. No. 3,981,246. In addition, by varying the axial stiffness of the sabot along its length, the double ramp design creates a more or less uniform axial shear stress at the sabot-projectile interface which maximizes load transfer between the sabot and the projectile.
Longitudinal grooves were used by Price, U.S. Pat. No. 4,326,464, to reduce the weight of a saddle back sabot while maintaining structural integrity and spatial position of the forward and aft boreriders. Similarly, Kraft, Foreign Patent No. DE 3704-027-A, teaches a reduced diameter saddle back sabot with lengthwise ribs between the annular guidance zones, or boreriders, to reduce the overall weight of the sabot without impairing its axial stiffness. However, both of these saddle back sabot designs may result in a decrease of transverse, or bending stiffness, and Price's invention may also suffer from decreased axial stiffness.
Romer, U.S. Pat. No. 4,608,927 (Foreign Patent No. DE 3314-749-A), teaches replacement of the front borerider in a double ramp sabot with fins to reduce overall weight. While maintaining proper axial stiffness to produce a uniform transfer of load, this design may actually impair overall transverse stiffness since a double ramp sabot is subject to bending of its tapered ends.
Romer also teaches the use of a synthetic material for all or part of the component fins. Sabot segments are generally fabricated from stiff metals, or fiber reinforced plastics (see Puckett, U.S. Pat. No. 4,958,571). Unreinforced synthetic materials tend to be more compliant than commonly used metals or composites, so it appears that Romer does not intend to teach the use of stiffer materials for its fins. In addition, because Romer's fins are not structural it is unlikely that a stiffer material would have been chosen.